A group of debilitating eye diseases, the “Glaucomas” represent the leading cause of preventable blindness in the United States and other developed nations. In general, glaucomas are characterized by the alteration of the trabecular meshwork (TM), which consists of specialized endothelial cells and their associated connective tissue. The TM endothelial cells line the path the aqueous humor of the eye filters through during the normal, physiological flux. The cells generate and regulate the TM by producing extracellular molecules, the composition of which is thought to directly control the aqueous fluid flow.
In Primary Open Angle Glaucoma (“POAG”), the most common form of glaucoma, an alteration in the TM leads to an obstruction of the normal ability of aqueous humor to leave its chamber surrounding the iris. However, the specific cells in the chamber between the iris and the cornea, in a region called the iridocorneal angle, remain “open” in that they continue to allow the egress of aqueous fluid (see, Vaughan, D. et al., In: General Ophthalmology, Appleton & Lange, Norwalk, Conn., pp. 213–230 (1992); and Gray's Anatomy, 37th Ed., Churchill Livingstone, London, pp. 1180–1190 (1989)). As a result of the alteration in the TM and the obstruction, an increased intraocular pressure (“IOP”) can be observed. IOP can result in progressive visual loss and blindness if not treated appropriately and in a timely fashion.
Glaucomas are estimated to affect between 0.4% and 3.3% of all adults over 40 years old (Leske, M. C. et al., Amer. J. Epidemiol. 113:1843–1846 (1986); Bengtsson, B., Br. J. Ophthamol. 73:483–487 (1989); Strong, N. P., Ophthal. Physiol. Opt. 12:3–7 (1992)). Moreover, the prevalence of the disease rises to over 6% of those 75 years or older (Strong, N. P., Ophthal. Physiol. Opt. 12:3–7 (1992)).
A link between steroid, corticosteroid, or glucocorticoid treatments and the increased IOP found in POAG disease has long been suspected. While only 5% of the normal population have high IOP increases in response to topical glucocorticoids, greater than 40–50% of similarly treated patients with POAG show a high IOP increase (16 mm Hg). In addition, an Open Angle Glaucoma may be induced by exposure to glucocorticoids. This observation has suggested that an increased or abnormal glucocorticoid response in trabecular cells of the TM may be involved in POAG (Zhan, G. L. et al., Exper. Eye Res. 54:211–218 (1992); Yun, A. J. et al., Invest. Ophthamol. Vis. Sci. 30:2012–2022 (1989); Clark, A. F., Exper. Eye Res. 55:265 (1992); Klemetti, A., Acta Ophthamol. 68:29–33 (1990); Knepper, P. A., U.S. Pat. No. 4,617,299).
The ability of glucocorticoids to induce a glaucoma-like condition has led to efforts to identify genes or gene products induced by the cells of the trabecular meshwork in response (Polansky, J. R. et al., In: Glaucoma Update IV, Springer-Verlag, Berlin, pp. 20–29 (1991); Polansky J. R. and Weinrob, R. N., In: Handbook of Experimetal Pharmacology, Vol. 69, Springer-Verlag, Berlin, pp. 461–538 (1984)). Initial efforts using short-term exposure to dexamethasone revealed only changes in specific protein synthesis. Extended exposure to relatively high levels of dexamethasone was, however, found to induce the expression of related 66 kD and 55 kD proteins that could be visualized by gel electrophoresis (Polansky, J. R. et al., In: Glaucoma Update IV, Springer-Verlag, Berlin, pp. 20–29 (1991)). The induction kinetics of these proteins as well as their dose response characteristics were similar to the kinetics that were required for steroid-induced IOP elevation in human subjects (Polansky, J. R. et al., In: Glaucoma Update IV, Springer-Verlag, Berlin, pp. 20–29 (1991)). Problems of aggregation and apparent instability or loss of protein in the purification process were obstacles in obtaining a direct protein sequence.
Nguyen et al., U.S. patent application Ser. No. 08/649,432, filed May 17, 1996, now U.S. Pat. No. 5,789,169, the entire disclosure of which is hereby incorporated by reference as if set forth at length herein, disclosed a novel protein sequence (the TIGR, trabecular meshwork inducible glucocorticoid response protein) highly induced by glucocorticoids in the endothelial lining cells of the human trabecular meshwork. Nguyen et al. also disclosed the cDNA sequence for that protein, the protein itself, molecules that bind to it, and nucleic acid molecules that encode it, and provided improved methods and reagents for diagnosing glaucoma and related disorders, as well as for diagnosing other diseases or conditions, such as cardiovascular, immunological, or other diseases or conditions that affect the expression or activity of the protein.
Because increased IOP is a readily measurable characteristic of glaucoma, the diagnosis of the disease is largely screened for by measuring intraocular pressure (tonometry) (Strong, N. P., Ophthal. Physiol. Opt. 12:3–7 (1992), Greve, M. et al., Can. J. Ophthamol. 28:201–206 (1993)). Unfortunately, because glaucomatous and normal pressure ranges overlap, such methods are of limited value unless multiple readings are obtained (Hitchings, R. A., Br. J. Ophthamol. 77:326 (1993); Tuck, M. W. et al., Ophthal. Physiol. Opt. 13:227–232 (1993); Vaughan, D. et al., In: General Ophthamology, Appleton & Lange, Norwalk, Conn., pp. 213–230 (1992); Vernon, S. A., Eye 7:134–137 (1993)). Patients may also have a differential sensitivity to optic nerve damage at a given IOP. For these reasons, additional methods, such as direct examination of the optic disk and determination of the extent of a patient's visual field loss are often conducted to improve the accuracy of diagnosis (Greve, M. et al., Can. J. Ophthamol. 28:201–206 (1993)). Moreover, these techniques are of limited prognostic value. In some aspects, the present invention fulfills the need for improved diagnostic and prognostic methods.
The elevation of intraocular pressure (IOP) due to topical corticosteroids (and other routes of administration) is an important clinical problem that limits the clinical use of these effective anti-inflammatory agents. If not observed in sufficient time, the IOP elevation (especially in certain individuals who show the high end of steroid-induced IOP elevations) can result in optic nerve damage and permanent visual field loss, termed “steroid glaucoma.” Even patients taking inhaled, nasal, rectal, and facial steroids may be at risk. The present invention, in part, provides improved diagnostic agents, prognostic agents, therapeutic agents and methods that address this clinical problem.